Liquid ejecting apparatus and liquid ejecting head

ABSTRACT

A liquid ejecting apparatus includes a liquid ejecting head that has an ejection surface including a first nozzle row configured to eject a first ink and a second nozzle row configured to eject a second ink. The liquid ejecting head is configured to be held in a first posture in which the ejection surface is inclined with respect to a horizontal plane. The dynamic surface tension of the first ink is higher than the dynamic surface tension of the second ink. In the first posture, the first nozzle row is positioned above the second nozzle row with respect to a gravity direction.

The present application is based on, and claims priority from JPApplication Serial Number 2021-140971, filed Aug. 31, 2021, thedisclosure of which is hereby incorporated by reference herein in itsentirety.

BACKGROUND 1. Technical Field

The present disclosure relates to a liquid ejecting apparatus and aliquid ejecting head.

2. Related Art

In a recording head that ejects a plurality of types of inks, anejection surface for ejecting an ink is inclined with respect to ahorizontal plane in some cases (for example, see JP-A-2014-34170).

The dynamic surface tension of an ink differs for each type of ink insome cases. In the related art, a relationship of a combination of aneffect of different dynamic surface tensions of the plurality of inksand an effect of a case where the ejection surface is inclined has notbeen considered.

SUMMARY

According to an aspect of the present disclosure, there is provided aliquid ejecting apparatus including a liquid ejecting head that has anejection surface including a first nozzle row for ejecting a first inkand a second nozzle row for ejecting a second ink, in which the liquidejecting head is configured to be held in a first posture in which theejection surface is inclined with respect to a horizontal plane. Adynamic surface tension of the first ink is higher than a dynamicsurface tension of the second ink. In the first posture, the firstnozzle row is positioned above the second nozzle row in a gravitydirection.

According to another aspect of the present disclosure, there is provideda liquid ejecting apparatus including a first liquid ejecting head thathas a first ejection surface including a first nozzle which ejects afirst ink and a second liquid ejecting head that has a second ejectionsurface including a second nozzle which ejects a second ink. A dynamicsurface tension of the first ink is higher than a dynamic surfacetension of the second ink. The first ejection surface is disposed suchthat an angle formed by an ejection direction of the first ink ejectedfrom the first nozzle and a gravity direction is a first angle, and thesecond ejection surface is disposed such that an angle formed by anejection direction of the second ink ejected from the second nozzle andthe gravity direction is a second angle larger than the first angle.

According to still another aspect of the present disclosure, there isprovided a liquid ejecting head including a first nozzle row that isused for ejecting a first ink, a second nozzle row that is used forejecting a second ink, and a third nozzle row that is used for ejectinga third ink. A dynamic surface tension of the third ink is lower than adynamic surface tension of the first ink and is higher than a dynamicsurface tension of the second ink. The third nozzle row is positionedbetween the first nozzle row and the second nozzle row in a gravitydirection.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a liquid ejecting apparatus accordingto a first embodiment.

FIG. 2 is a block diagram showing an ink flow path.

FIG. 3 is a bottom view showing a nozzle plate on which a nozzle row isformed.

FIG. 4 is a schematic view showing a liquid ejecting head in an inclinedposture in which an ejection surface is inclined with respect to ahorizontal plane and is a view showing a water head difference of thenozzle row.

FIG. 5 is a cross-sectional view showing a nozzle plate according tocomparative example 1 and is a view showing a state where ink dropletsoverflow from a nozzle.

FIG. 6 is a cross-sectional view showing the nozzle plate according tocomparative example 1 and is a view showing a state where the inkdroplets overflowed from the nozzle drip along the ejection surface.

FIG. 7 is a cross-sectional view showing a nozzle plate according toexample 1 and is a view showing a state where the ink droplets overflowfrom the nozzle.

FIG. 8 is a schematic view showing a liquid ejecting head according toexample 2 and is a view showing the inclined posture in which theejection surface is inclined to face obliquely upward.

FIG. 9 is a schematic view showing a liquid ejecting head according toexample 3 and is a view showing a posture in which the ejection surfaceis perpendicular to the horizontal plane.

FIG. 10 is a schematic view showing a liquid ejecting apparatusaccording to example 4.

FIG. 11 is a schematic view showing a liquid ejecting apparatusaccording to example 5.

FIG. 12 is a schematic view showing a liquid ejecting apparatusaccording to example 6.

FIG. 13 is a table showing components of an ink according to an example.

FIG. 14 is a bottom view showing an ejection surface of a liquidejecting head according to modification example 1.

FIG. 15 is a bottom view showing an ejection surface of a liquidejecting head according to modification example 2.

FIG. 16 is a bottom view showing an ejection surface of a liquidejecting head according to modification example 3.

FIG. 17 is a bottom view showing an ejection surface of a liquidejecting head according to modification example 4.

FIG. 18 is a schematic view showing a liquid ejecting apparatusaccording to a second embodiment.

FIG. 19 is a schematic view showing disposition of the liquid ejectinghead.

FIG. 20 is a schematic view showing disposition of the liquid ejectinghead.

FIG. 21 is a schematic view showing disposition of the liquid ejectinghead.

FIG. 22 is a schematic view showing disposition of the liquid ejectinghead.

FIG. 23 is a schematic view showing disposition of the liquid ejectinghead.

DESCRIPTION OF EXEMPLARY EMBODIMENTS

Hereinafter, embodiments for carrying out the present disclosure will bedescribed with reference to the drawings. However, in each drawing, thedimensions and scale of each portion are different from the actualdimensions and scale as appropriate in some cases. In addition, sincethe embodiments to be described below are suitable specific examples ofthe present disclosure, various technically preferable limitations areattached, but the scope of the present disclosure is not limited to theforms unless stated otherwise to limit the present disclosure in thefollowing description.

In the following description, three directions intersecting each otherwill be described as an X-axis direction, a Y-axis direction, and aZ-axis direction in some cases. The X-axis direction includes an X1direction and an X2 direction which are directions opposite to eachother. The X-axis direction is an example of a first direction. TheY-axis direction includes a Y1 direction and a Y2 direction which aredirections opposite to each other. The Y-axis direction is an example ofa second direction. The Z-axis direction includes a Z1 direction and aZ2 direction which are directions opposite to each other. The X-axisdirection, the Y-axis direction, and the Z-axis direction are orthogonalto each other. The Y-axis direction and the Z-axis direction aredirections having an ejection surface F1 to be described later asreference.

In addition, a downward direction of a gravity direction will bedescribed as a gravity direction G1, and a direction orthogonal to bothof the gravity direction G1 and the X-axis direction will be describedas a K-axis direction. In addition, an opposite direction to the gravitydirection G1 will be defined as an upward direction G2. The K-axisdirection includes a K1 direction and a K2 direction which aredirections opposite to each other. The K-axis direction is an example ofa third direction. The K-axis direction is an example of a horizontaldirection. The horizontal direction is a direction orthogonal to thegravity direction G1. The third direction is a direction orthogonal toboth of the first direction and the gravity direction G1.

FIG. 1 is a schematic view showing a liquid ejecting apparatus 1according to a first embodiment. FIG. 2 is a block diagram showing anink flow path. The liquid ejecting apparatus 1 is an ink jet typeprinting apparatus that ejects an ink, which is an example of a“liquid”, to a medium PA as ink droplets. The liquid ejecting apparatus1 is a so-called line type printing apparatus in which a plurality ofnozzles ejecting an ink are distributed over the entire range in a widthdirection of the medium PA. The medium PA is typically printing paper.The medium PA is not limited to the printing paper and may be, forexample, a printing target made of any material such as a resin film andcloth.

The liquid ejecting apparatus 1 includes a liquid ejecting head 10 thathas the ejection surface F1 inclined with respect to a horizontal planeF0. The liquid ejecting apparatus 1 includes a plurality of liquidcontainers 2, a control unit 3, a medium transporting mechanism 4, anink supply unit 5, and the liquid ejecting head 10. The liquid ejectingapparatus 1 may include one liquid ejecting head 10 or may include aplurality of liquid ejecting heads 10. The liquid ejecting apparatus 1of the present embodiment includes one liquid ejecting head 10. When theplurality of liquid ejecting heads 10 are included, the plurality ofliquid ejecting heads 10 are arranged in the X-axis direction toconfigure a line head.

The control unit 3 controls an operation of each element of the liquidejecting apparatus 1. The control unit 3 includes, for example, aprocessing circuit such as a CPU and an FPGA and a storage circuit suchas a semiconductor memory. The storage circuit stores various types ofprograms and various types of data. The processing circuit realizesvarious types of control by executing the program and using the data asappropriate. The CPU is an abbreviation for a central processing unit.The FPGA is an abbreviation for a field programmable gate array.

The medium transporting mechanism 4 is controlled by the control unit 3and transports the medium PA in a transport direction DM. The transportdirection DM is a transport direction of the medium PA at a positionfacing the ejection surface F1 and is parallel to or substantiallyparallel to the Y-axis direction. The medium transporting mechanism 4includes a transport roller that is long along the width direction ofthe medium PA and a motor that rotates the transport roller. The mediumtransporting mechanism 4 is not limited to the configuration using thetransport roller and may have, for example, a configuration using a drumor an endless belt that transports the medium PA in a state where themedium PA is adsorbed to an outer peripheral surface because of anelectrostatic force.

A medium transport path 4 a through which the medium PA is transportedis formed in the liquid ejecting apparatus 1. The medium transport path4 a is a path from a feeding portion 4 b to a discharging portion 4 c.The medium transporting mechanism 4 transports the medium PA along themedium transport path 4 a. The feeding portion 4 b and the dischargingportion 4 c include a tray capable of storing the medium PA.

The liquid container 2 stores an ink. Examples of a specific embodimentof the liquid container 2 include a cartridge that can beattached/detached with respect to the liquid ejecting apparatus 1, abag-shaped ink pack formed of a flexible film, and an ink tank that canbe refilled with an ink. A type of ink to be stored in the liquidcontainer 2 can be any type.

The liquid container 2 includes liquid containers 2A, 2B, 2C, and 2D.The liquid container 2A stores a first ink. The liquid container 2Bstores a second ink. The liquid container 2C stores a third ink. Theliquid container 2D stores a fourth ink. For example, the first ink, thesecond ink, the third ink, and the fourth ink are inks having colorsdifferent from each other. The first ink, the second ink, the third ink,and the fourth ink have dynamic surface tensions different from eachother. The dynamic surface tension of the first ink is higher than thedynamic surface tension of the second ink. The dynamic surface tensionof the third ink is lower than the dynamic surface tension of the firstink and is higher than the dynamic surface tension of the second ink.The dynamic surface tension of the fourth ink is lower than the dynamicsurface tension of the third ink and is higher than the dynamic surfacetension of the second ink. A component for each type of ink andmeasurement of a dynamic surface tension will be described later.

A difference between the dynamic surface tension of the first ink andthe dynamic surface tension of the second ink is 1.0 mN/m or larger.When a lifetime is set to 10 msec in measurement of a dynamic surfacetension to be described later, the dynamic surface tension of the firstink is higher than the dynamic surface tension of the second ink. Whenthe lifetime is set to 10 msec, the dynamic surface tension of the firstink is higher than that of the third ink, the dynamic surface tension ofthe third ink is higher than that of the fourth ink, and the dynamicsurface tension of the fourth ink is higher than that of the second ink.

The ink supply unit 5 has ink flow paths 6 and 7, through which an inkis supplied from the liquid containers 2 to the liquid ejecting head 10,and a pressure adjusting portion 8 that adjusts the pressure of an inkin the liquid ejecting head 10. The ink flow path 6 includes a flow pathfrom the liquid containers 2 to the pressure adjusting portion 8. Theink flow path 7 includes a flow path from the pressure adjusting portion8 to the liquid ejecting head 10. The ink flow path 7 includes a flowpath formed in the liquid ejecting head 10. The ink flow paths 6 and 7include, for example, a flow path member, a pipe, and a tube in which agroove, a recessed portion, or a through-hole is formed.

The pressure adjusting portion 8 adjusts the pressure of an ink to besupplied to the liquid ejecting head 10 such that a predeterminedpressure acts on a nozzle N. The pressure adjusting portion 8 is, forexample, a negative pressure generating portion including a pressureadjusting valve. The negative pressure generating portion may beconfigured, for example, to have the pressure adjusting valve thatopens/closes the ink flow path and a flexible member that bends based ona differential pressure between the pressure of the ink flow pathdownstream of the pressure adjusting valve and the atmospheric pressureand to control the opening/closing of the pressure adjusting valve suchthat a negative pressure in a predetermined range acts on the nozzle Nas the pressure adjusting valve is moved because of the bending of theflexible member.

In addition, the pressure adjusting portion 8 may adjust the pressure ofan ink to be supplied to the liquid ejecting head 10 with a sub-tankthat temporarily stores the ink. Specifically, the pressure adjustingportion 8 may have the sub-tank and any sensor that can detect a storedamount of an ink in the sub-tank and adjust the pressure of an ink inthe liquid ejecting head 10 by a water head difference between a liquidsurface in the sub-tank and the liquid ejecting head 10 by keeping thestored amount of the ink in the sub-tank substantially constant, thatis, keeping the liquid surface of the ink stored in the sub-tanksubstantially constant as the ink is refilled from the liquid containers2 once the stored amount of the ink in the sub-tank detected by thesensor has become smaller than a threshold. In addition, the pressure ofthe ink to be supplied to the liquid ejecting head 10 may be adjusted bysetting a pressure in the sub-tank to a predetermined pressure with acompressor.

The pressure adjusting portion 8 includes pressure adjusting portions8A, 8B, 8C, and 8D. The pressure adjusting portion 8A communicates withthe liquid container 2A and adjusts the pressure of the first ink. Thepressure adjusting portion 8B communicates with the liquid container 2Band adjusts the pressure of the second ink. The pressure adjustingportion 8C communicates with the liquid container 2C and adjusts thepressure of the third ink. The pressure adjusting portion 8Dcommunicates with the liquid container 2D and adjusts the pressure ofthe fourth ink.

FIG. 3 is a bottom view showing a nozzle plate 11 on which a nozzle rowNL is formed. The liquid ejecting head 10 includes the nozzle plate 11having a plurality of nozzle rows NL. The nozzle row NL includes aplurality of nozzles N ejecting an ink. Among surfaces of the nozzleplate 11, a surface facing the medium PA is the ejection surface F1 forejecting the ink. The plurality of nozzles N are formed in the ejectionsurface F1. The ejection surface F1 is disposed to be spaced apart fromthe medium PA.

The plurality of nozzle rows NL include nozzle rows NLA, NLB, NLC, andNLD. The nozzle row NLA includes the plurality of nozzles N ejecting thefirst ink. The nozzle row NLB includes the plurality of nozzles Nejecting the second ink. The nozzle row NLC includes the plurality ofnozzles N ejecting the third ink. The nozzle row NLD includes theplurality of nozzles N ejecting the fourth ink. When not distinguishingbetween the nozzle rows NLA, NLB, NLC, and NLD, the nozzle rows will bedescribed as the nozzle rows NL in some cases.

The nozzle row NL includes the plurality of nozzles N arranged in theX-axis direction. The nozzle N is a through-hole that penetrates thenozzle plate 11 in a plate thickness direction thereof. The platethickness direction of the nozzle plate 11 follows the Z-axis direction.The nozzle rows NLA, NLB, NLC, and NLD are disposed at positionsdifferent from each other in the Y-axis direction.

The nozzle row NLA, the nozzle row NLC, the nozzle row NLD, and thenozzle row NLB are disposed in this order toward the Y1 direction. Thenozzle row NLA, the nozzle row NLC, the nozzle row NLD, and the nozzlerow NLB are spaced apart from each other in the Y-axis direction. Thenozzle row NLC is disposed between the nozzle row NLA and the nozzle rowNLB in the Y-axis direction. The nozzle row NLD is disposed between thenozzle row NLC and the nozzle row NLB in the Y-axis direction.

When viewed in the Y-axis direction, the nozzle row NLA, the nozzle rowNLC, the nozzle row NLD, and the nozzle row NLB at least partiallyoverlap each other. In the present embodiment, when viewed in the Y-axisdirection, the nozzle row NLA, the nozzle row NLC, the nozzle row NLD,and the nozzle row NLB entirely overlap each other.

As shown in FIG. 1 , the liquid ejecting head 10 is held, for example,in an inclined posture with respect to a housing 1 a of the liquidejecting apparatus 1. “The liquid ejecting head 10 is held with respectto the housing 1 a of the liquid ejecting apparatus 1” includes both ofa case where the liquid ejecting head 10 is held by being directly fixedto the housing 1 a and a case where the liquid ejecting head 10 isindirectly held with respect to the housing 1 a via a member differentfrom the housing 1 a. The liquid ejecting apparatus 1 can hold theliquid ejecting head 10 in the inclined posture in which the ejectionsurface F1 is inclined with respect to the horizontal plane F0.

FIG. 4 is a schematic view showing the liquid ejecting head 10 in theinclined posture in which the ejection surface F1 is inclined withrespect to the horizontal plane F0 and is a view showing water headdifferences H1 to H4 of the nozzle rows NL. As shown in FIG. 4 , theejection surface F1 of the liquid ejecting head 10 is inclined withrespect to the horizontal plane F0 at an inclination angle θ1. Theinclination angle θ1 is, for example, an acute angle that is less than90 degrees. The inclination angle θ1 may be an obtuse angle exceeding 90degrees. The inclination angle θ1 may be 90 degrees. The inclinationreferred herein includes 90 degrees. The inclined posture of the liquidejecting head 10 in which the ejection surface F1 is inclined withrespect to the horizontal plane F0 at the inclination angle θ1 is anexample of a first posture.

In the inclined posture of the liquid ejecting head 10 shown in FIG. 4 ,the plurality of nozzle rows NL are disposed at heights different fromeach other in the gravity direction G1. The nozzle row NLA is disposedat a height position HA, and the nozzle row NLB is disposed at a heightposition HB. The height position HA is positioned above the heightposition HB. That is, the nozzle row NLA for ejecting the first inkhaving a higher dynamic surface tension is positioned above the nozzlerow NLB for ejecting the second ink having a lower dynamic surfacetension.

The nozzle row NLC is disposed at a height position HC. The heightposition HC is below the height position HA and is above the heightposition HB. In the inclined posture of the liquid ejecting head 10, thenozzle row NLC is positioned below the nozzle row NLA and above thenozzle row NLB. That is, the nozzle row NLC for ejecting the third inkhaving the second highest dynamic surface tension, among the first ink,the second ink, and the third ink, is disposed between the nozzle rowNLA and the nozzle row NLB in the gravity direction G1.

The nozzle row NLD is disposed at a height position HD. The heightposition HD is below the height position HC and is above the heightposition HB. In the inclined posture of the liquid ejecting head 10, thenozzle row NLD is positioned below the nozzle row NLC and above thenozzle row NLB. That is, the nozzle row NLD for ejecting the fourth inkhaving the second highest dynamic surface tension, among the second ink,the third ink, and the fourth ink, is disposed between the nozzle rowNLC and the nozzle row NLB in the gravity direction G1.

As shown in FIG. 4 , when viewed in the X-axis direction, the nozzle rowNLA, the nozzle row NLC, the nozzle row NLD, and the nozzle row NLB aredisposed at intervals from each other.

When comparing the plurality of nozzle rows NL to each other, the nozzlerow NL for ejecting an ink having a higher dynamic surface tension ispositioned above the nozzle row NL for ejecting an ink having a lowerdynamic surface tension.

Next, a case where ink droplets 101 and 102 drip along the ejectionsurface F1 as the meniscus of the nozzle N has a positive pressure dueto a factor such as circulation cleaning in which an abnormality occursin the pressure adjusting portion 8 and an ink is circulated in the flowpath in the liquid ejecting head 10 by a circulation mechanism (notshown) will be described with reference to FIGS. 5 to 7 . Herein, thenozzle plates 11 and 111 for ejecting two types of inks having dynamicsurface tensions different from each other will be described asexamples. FIGS. 5 and 6 show the nozzle plate 111 according tocomparative example 1, and FIG. 7 shows the nozzle plate 11 according toexample 1. In the nozzle plate 111 according to comparative example 1,the nozzle row NLB for ejecting the second ink having a lower dynamicsurface tension is positioned above the nozzle row NLA for ejecting thefirst ink having a higher dynamic surface tension. In the nozzle plate11 according to example 1, contrary to the case of comparative example1, the nozzle row NLA for ejecting the first ink is positioned above thenozzle row NLB for ejecting the second ink.

FIG. 5 is a cross-sectional view showing a state where the ink droplets101 and 102 overflow from the nozzles NA and NB of the nozzle plate 111according to comparative example 1. In the state shown in FIG. 5 , theink droplet 102, which is the second ink, overflows from the nozzle rowNLB above, and the ink droplet 101, which is the first ink, overflowsfrom the nozzle row NLA below.

FIG. 6 is a cross-sectional view showing the nozzle plate 111 accordingto comparative example 1 and is a view showing a state where the inkdroplet 101 overflowed from the nozzle NA drips along the ejectionsurface F1. In the state shown in FIG. 6 , the ink droplet 102 moves inthe Y1 direction along the ejection surface F1. The ink droplet 101overflowed from the nozzle row NLA below is at the front of the nozzleNA. The front of the nozzle NA is outside the nozzle NA and is aposition of the nozzle NA in the Z1 direction. The ink droplet 102having a lower dynamic surface tension is likely to drip lower than theink droplet 101 having a higher dynamic surface tension due to gravity.The ink droplet 102 moves in the Y1 direction and approaches the inkdroplet 101 below. With the passage of time, the ink droplet 102 movesin the Y1 direction, and comes into contact with the ink droplet 101.Thus, the ink droplet 102 and the ink droplet 101 are mixed with eachother.

In the state, when the first ink is ejected from the nozzle row NLA, thefirst ink mixed with the second ink lands on the medium PA. For thisreason, there is a possibility that printing accuracy decreases.

FIG. 7 is a cross-sectional view showing the nozzle plate 11 accordingto example 1 and shows a state where the ink droplets 101 and 102overflow from the nozzles NA and NB. In the state shown in FIG. 7 , theink droplet 102 moves in the Y1 direction along the ejection surface F1.In this case, the ink droplet 101 overflowed from the nozzle row NLAabove remains to be at a position at the front of the nozzle NA. The inkdroplet 101 above does not approach the nozzle row NLB below. The inkdroplet 102 overflowed from the nozzle row NLB below moves downward dueto gravity, but the ink droplet 102 does not approach the ink droplet101. The ink droplet 101 and the ink droplet 102 are not mixed with eachother. As described above, since the nozzle row NLA for ejecting thefirst ink having a higher dynamic surface tension is positioned abovethe nozzle row NLB in the gravity direction G1, color mixing between thefirst ink and the second ink can be suppressed in example 1.

In the liquid ejecting head 10 according to the first embodiment shownin FIG. 4 , the nozzle rows NLA, NLB, NLC, and NLD are disposedaccording to the dynamic surface tension of an ink. The nozzle row NLAfor ejecting the first ink having the highest dynamic surface tension isdisposed at a position higher than the other nozzle rows NLB, NLC, andNLD in the gravity direction G1. As described above, since the nozzlerow NLA for ejecting the first ink, which is most unlikely to dripdroplets, is disposed at a higher position, the first ink, the othersecond ink, the third ink, and the fourth ink are prevented from beingmixed with each other.

In the liquid ejecting head 10, the nozzle row NLB for ejecting thesecond ink having the lowest dynamic surface tension is disposed at aposition lower than the other nozzle rows NLA, NLC, and NLD in thegravity direction G1. As described above, since the nozzle row NLB forejecting the second ink, which is most likely to drip droplets, isdisposed at a lower position, the second ink, the other first ink, thethird ink, and the fourth ink are prevented from being mixed with eachother.

As for a plurality of types of inks, since the nozzle row NLA forejecting the first ink having a higher dynamic surface tension ispositioned above the nozzle row NLB for ejecting the second ink having alower dynamic surface tension in the gravity direction G1, the mixing ofthe inks is suppressed in the liquid ejecting head 10. As a result, theprinting accuracy of the liquid ejecting apparatus 1 can be improved.Compared to the configuration of comparative example 1 in which thenozzle row NLB for ejecting the second ink having a lower dynamicsurface tension is disposed at a position higher than the nozzle row NLAfor ejecting the first ink having a higher dynamic surface tension, aprobability that the plurality of inks can be mixed in the liquidejecting head 10 is low.

Next, the water head differences H1 to H4 of the nozzle rows NL will bedescribed with reference to FIG. 4 . FIG. 4 shows a height position H0of the pressure adjusting portion 8 in the gravity direction G1. Theheight position H0 is positioned above the height positions HA, HB, HC,and HD of the nozzle rows NLA, NLB, NLC, and NLD. As described above,the height position HA is disposed at a position higher than the heightposition HC, HC is disposed at a position higher than the heightposition HD, and the height position HD is disposed at a position higherthan the height position HB. The height position H0 of the pressureadjusting portion 8 is not limited to being above the height positionsof the nozzle rows NLA, NLB, NLC, and NLD. The height position H0 of thepressure adjusting portion 8 may be below the height positions of thenozzle rows NLA, NLB, NLC, and NLD. In addition, the height position H0of the pressure adjusting portion 8 may be a height position between thenozzle row NLA and the nozzle row NLB. In addition, all of the heightpositions of the plurality of pressure adjusting portions 8A, 8B, 8C,and 8D are the height position H0.

A water head difference H2 between the pressure adjusting portion 8 andthe nozzle row NLB is larger than a water head difference H4 between thepressure adjusting portion 8 and the nozzle row NLD. The water headdifference H4 between the pressure adjusting portion 8 and the nozzlerow NLD is larger than a water head difference H3 between the pressureadjusting portion 8 and the nozzle row NLC. The water head difference H3between the pressure adjusting portion 8 and the nozzle row NLC islarger than a water head difference H1 between the pressure adjustingportion 8 and the nozzle row NLA.

In the inclined posture of the liquid ejecting head 10 shown in FIG. 4 ,the water head differences H1, H2, H3, and H4 acting on the nozzle rowsNL are different from each other according to a height position. When awater head difference is larger, an ink is more likely to be supplied tothe nozzle row NL compared to a case of a smaller water head difference.When comparing the nozzle row NLA and the nozzle row NLB to each other,an ink is more unlikely to be supplied to the nozzle row NLA having asmaller water head difference H1 than the nozzle row NLB having a largerwater head difference H2.

In addition, for example, when dynamic surface tensions of a pluralityof types of inks are different from each other, a capillary force actingon an ink and a meniscus pressure resistance are different for thenozzle N. A capillary force acting on the first ink having a higherdynamic surface tension is larger than a capillary force acting on thesecond ink having a lower dynamic surface tension. The meniscus pressureresistance of the first ink having a higher dynamic surface tension isgreater than the meniscus pressure resistance of the second ink having alower dynamic surface tension. The first ink having a higher dynamicsurface tension is more easily supplied to the nozzle row NL than thesecond ink having a lower dynamic surface tension.

That is, since a difference in the dynamic surface tension of an inkaffects variations in ease of supplying the ink to the nozzle row NL, byassigning an ink having a different dynamic surface tension according tothe height of the nozzle row NL in order to alleviate variations in easeof supplying the ink to the nozzle row NL caused by variations in thewater head difference, variations in ease of supplying the ink into thenozzle row NL can be reduced, and as a result, variations in ejectioncharacteristics can be reduced. Examples of the ejection characteristicsinclude a weight Iw and a speed Vm of ejected droplets.

In the liquid ejecting apparatus according to the related art, arelationship of a combination of an effect of different dynamic surfacetensions and an effect of the inclined ejection surface F1 of the liquidejecting head 10 has not been considered. When the fact that a dynamicsurface tension is different for each ink and the ejection surface F1 isinclined is not considered, a problem, in which a difference in ejectioncharacteristics of an ink for each nozzle row NL becomes large, occurs.

For example, when each of the pressure adjusting portions 8corresponding to each of the plurality of nozzle rows NL has the commonconfiguration and when each distance (water head difference) betweeneach nozzle row NL and each pressure adjusting portion 8 correspondingto each nozzle row NL in the gravity direction is equal, a pressure(negative pressure) acting on each nozzle row NL is the same. However,when the liquid ejecting head 10 is inclined, as the plurality of nozzlerows NL are disposed at positions different from each other in thegravity direction, variations in each water head difference occur.Further, there is a difference in the dynamic surface tension of eachink, and there is a possibility that variations occur in a pressureacting on each nozzle row NL.

Then, when the first ink that is easier to be supplied is supplied tothe nozzle row NLB to which the first ink is easier to be supplied andthe second ink that is more difficult to be supplied is supplied to thenozzle row NLA to which the second ink is more difficult to be supplied,a large difference between the ejection characteristics of the nozzlerow NLA and the ejection characteristics of the nozzle row NLB occurs.In addition, in this case, there is also a possibility that bubbles aredrawn from the nozzle N as a relatively large negative pressure acts onthe meniscus of the nozzle row NLA or a possibility that an inkoverflows from the nozzle N and the meniscus is destroyed as arelatively large positive pressure acts on the meniscus of the nozzlerow NLB.

In the liquid ejecting head 10 of the present embodiment, the nozzlerows NLA, NLB, NLC, and NLD are disposed according to the dynamicsurface tension of an ink. The nozzle row NLA for ejecting the first inkhaving the highest dynamic surface tension is disposed at a positionhigher than the other nozzle rows NLB, NLC, and NLD in the gravitydirection G1. The first ink that is easier to be supplied is supplied tothe nozzle row NLA having a smaller water head difference H1.

In the liquid ejecting head 10, the nozzle row NLB for ejecting thesecond ink having the lowest dynamic surface tension is disposed at aposition lower than the other nozzle rows NLA, NLC, and NLD in thegravity direction G1. The second ink that is more difficult to besupplied is supplied to the nozzle row NLB having a larger water headdifference H2.

In the liquid ejecting head 10, as for a plurality of types of inks,since the nozzle row for ejecting the first ink having a higher dynamicsurface tension is positioned above the nozzle row for ejecting thesecond ink having a lower dynamic surface tension in the gravitydirection G1, variations in ease of supplying an ink can be reduced, andvariations in ejection characteristics of an ink in a plurality ofnozzle rows can be suppressed. As a result, the printing accuracy of theliquid ejecting apparatus 1 can be improved.

In addition, in the liquid ejecting apparatus 1, since the plurality ofpressure adjusting portions 8 are disposed at the same height positionH0 in the gravity direction G1, the liquid ejecting apparatus 1 can beminiaturized, and the structure of the liquid ejecting apparatus 1 canbe simplified, compared to a case where the height positions of theplurality of pressure adjusting portions 8 are different from eachother. By aligning the height positions H0 of the plurality of pressureadjusting portions 8, the ink flow path can be simplified.

Next, the inclined posture of the liquid ejecting head 10 according toexample 2 will be described with reference to FIG. 8 . FIG. 8 is aschematic view showing the liquid ejecting head 10 according to example2 and is a view showing the inclined posture in which the ejectionsurface F1 is inclined to face obliquely upward. The liquid ejectinghead 10 according to example 2 shown in FIG. 8 is different from theliquid ejecting head 10 of the first embodiment shown in FIG. 4 in thatan inclination angle θ2 of the ejection surface F1 is different from theinclination angle θ1.

The inclination angle θ2 is an angle larger than 90 degrees with respectto the horizontal plane F0 and is an obtuse angle. The inclination angleθ2 is a rotation angle counterclockwise shown in the drawing with arotation shaft along the X-axis direction as a center. In FIG. 8 , theejection surface F1 is inclined to face obliquely upward. Such a liquidejecting head 10 according to example 2 can achieve the same operationaleffects as the liquid ejecting head 10 according to the firstembodiment, and variations in ejection characteristics of an ink of theplurality of nozzle rows can be suppressed.

Next, the inclined posture of the liquid ejecting head 10 according toexample 3 will be described with reference to FIG. 9 . FIG. 9 is aschematic view showing the liquid ejecting head 10 according to example3 and is a view showing a posture in which the ejection surface F1 isperpendicular to the horizontal plane F0. The liquid ejecting head 10according to example 3 shown in FIG. 9 is different from the liquidejecting head 10 of the first embodiment shown in FIG. 4 in that anangle θ3 of the ejection surface F1 is different from the inclinationangle θ1. The inclined posture of the liquid ejecting head 10 mayinclude a posture perpendicular to the horizontal plane F0. In thepresent embodiment, a case where the ejection surface F1 isperpendicular to the horizontal plane F0 is referred to as beinginclined in some cases. The angle θ3 forms a right angle with respect tothe horizontal plane F0, which is 90 degrees. Such a liquid ejectinghead 10 according to example 3 can achieve the same operational effectsas the liquid ejecting head 10 according to the first embodiment, andvariations in ejection characteristics of an ink of the plurality ofnozzle rows can be suppressed by reducing variations in ease ofsupplying an ink.

Next, a posture change of the liquid ejecting head 10 according toexample 4 will be described with reference to FIG. 10 . FIG. 10 is aschematic view showing the liquid ejecting head 10 according to example4. In FIG. 10 , the liquid ejecting head 10 in a first posture P1 inwhich the ejection surface F1 is inclined with respect to the horizontalplane F0 is shown by a solid line, and the liquid ejecting head 10 in asecond posture P2 in which the ejection surface F1 is disposed along thehorizontal plane F0 is shown by a broken line. The liquid ejecting head10 can rotationally move around a rotation shaft S1 extending in theX-axis direction.

The posture of the liquid ejecting head 10 can be changed to a pluralityof postures including the first posture P1 and the second posture P2.The liquid ejecting apparatus 1 according to example 4 has a posturechanging mechanism 13 that changes the posture of the liquid ejectinghead 10. The posture changing mechanism 13 includes a bearing 14 thatholds the rotation shaft S1 extending in the X-axis direction and adrive mechanism 15 that rotates the rotation shaft S1. The bearing 14rotatably supports the rotation shaft S1. The drive mechanism 15includes, for example, a motor.

In FIG. 10 , imaginary lines L1 and L2 are shown by two-dot chain lines.The imaginary line L1 is an imaginary straight line that passes througha center C1 between the nozzle row NLA and the nozzle row NLB and thatextends in a direction perpendicular to the ejection surface F1 in thefirst posture P1. The imaginary line L1 extends in the Z-axis directionwhen viewed in the X-axis direction. When the liquid ejecting head 10 isin the first posture P1, the rotation shaft S1 is positioned closer tothe nozzle row NLB when viewed from the imaginary line L1. In otherwords, when the liquid ejecting head 10 is in the first posture P1, therotation shaft S1 is positioned closer to the nozzle row NLB than theimaginary line L1 is in the Y-axis direction.

The imaginary line L2 is an imaginary straight line that passes throughthe center C1 between the nozzle row NLA and the nozzle row NLB and thatextends in the direction perpendicular to the ejection surface F1 in thesecond posture P2. The imaginary line L2 extends in the Z-axis directionwhen viewed in the X-axis direction. In FIG. 10 , arrows indicating theX-axis direction, the Y-axis direction, and the Z-axis direction in thesecond posture P2 are shown by broken lines. The first posture P1 andthe second posture P2 are shifted from each other by the inclinationangle θ1 when viewed in the X-axis direction. When the liquid ejectinghead 10 is in the second posture P2, the rotation shaft S1 is positionedcloser to the nozzle row NLB when viewed from the imaginary line L2. Inother words, when the liquid ejecting head 10 is in the second postureP2, the rotation shaft S1 is positioned closer to the nozzle row NLBthan the imaginary line L2 is in the Y-axis direction.

In the first posture P1 and the second posture P2, the rotation shaft S1may be at the same position or may be at different positions. In theposture change of the liquid ejecting head 10 from the first posture P1to the second posture P2, the liquid ejecting head 10 may include alinear movement. The liquid ejecting apparatus 1 can linearly move thebearing 14 that holds the rotation shaft S1. For example, the liquidejecting apparatus can linearly move the bearing with a rack and pinion.The liquid ejecting head 10 can be linearly moved using other ballscrews, guide grooves, actuators, and belt mechanisms.

Next, a centrifugal force acting on a meniscus during the rotationalmovement of the liquid ejecting head 10 will be described. When theliquid ejecting head 10 rotationally moves around the rotation shaft S1,a centrifugal force acts on menisci in the plurality of nozzle rows NL.Radius of gyration RA from the rotation shaft S1 to the nozzle row NLAis larger than radius of gyration RB from the rotation shaft S1 to thenozzle row NLB. During the rotational movement of the liquid ejectinghead 10, the magnitude of a centrifugal force acting on the meniscus ofthe nozzle row NLA and the magnitude of a centrifugal force acting onthe meniscus of the nozzle row NLB are different from each other. Duringthe rotational movement of the liquid ejecting head 10, the magnitude ofthe centrifugal force acting on the meniscus of the nozzle row NLA isgreater than the magnitude of the centrifugal force acting on themeniscus of the nozzle row NLB.

A centrifugal force that acts immediately after the start of therotational movement of the liquid ejecting head 10 acts such that ameniscus in the nozzle N is moved toward the outside of the nozzle. Inother words, the centrifugal force acts to move the meniscus in adirection separating away from the rotation shaft S1. In addition, aninertial force caused by the centrifugal force acts on a meniscusobtained by moving the meniscus in the nozzle N toward the outside ofthe nozzle with the centrifugal force. The inertial force caused by thecentrifugal force is a force that moves the meniscus in the nozzle N. Inother words, the inertial force caused by the centrifugal force is aforce acting on the meniscus in a direction approaching the rotationshaft S1. There is a possibility that the meniscus jumps out of thenozzle N or the meniscus is dented and bubbles in the nozzle N are drawnbecause of such a centrifugal force and the inertial force caused by thecentrifugal force.

When the dynamic surface tension of an ink is the same, the nozzle rowNLA having a larger centrifugal force has a higher probability that themeniscus disintegrates than the nozzle row NLB having a smallercentrifugal force. In the liquid ejecting head 10, the first ink havinga higher dynamic surface tension is supplied to the nozzle row NLA, andthe second ink having a lower dynamic surface tension is supplied to thenozzle row NLB. The first ink is supplied to the nozzle row NLA having alarger centrifugal force, and the second ink is supplied to the nozzlerow NLB having a smaller centrifugal force. Accordingly, since the firstink having a higher dynamic surface tension is supplied to a nozzlehaving a larger centrifugal force, the disintegration of a meniscus canbe suppressed.

In the liquid ejecting head 10, among a plurality of types of inks, anink having a higher dynamic surface tension is supplied to the nozzlerow NL having a larger centrifugal force, and an ink having a lowerdynamic surface tension is supplied to the nozzle row NL having asmaller centrifugal force. Accordingly, the disintegration of a meniscusof an ink in the nozzle N is suppressed.

In the liquid ejecting head 10, by suppressing the disintegration of ameniscus, the entry of bubbles into the nozzle N of the nozzle row NLAis suppressed, or the leakage of an ink from the nozzle N of the nozzlerow NLA is suppressed.

The liquid ejecting head 10 according to example 4 includes theplurality of nozzle rows NL, each of which extends in the X-axisdirection, but may include the nozzle row NL extending in a directionintersecting an X-axis in plan view of the ejection surface F1 towardthe Z-axis direction. In this case, radius of gyration from the rotationshaft S1 to the nozzle row NL may be a distance between the nozzle Nthat is most separated from the rotation shaft S1, among the pluralityof nozzles N configuring the nozzle row NL, and the rotation shaft S1when viewed in the X-axis direction.

Next, the liquid ejecting head 10 according to example 5 will bedescribed with reference to FIG. 11 . FIG. 11 is a schematic viewshowing a cap 22 covering the liquid ejecting head 10 of the liquidejecting apparatus 1 according to example 5 and the ejection surface F1of the liquid ejecting head 10. The liquid ejecting apparatus 1 canperform a maintenance operation. The liquid ejecting apparatus 1performs the maintenance operation in the second posture P2 of theliquid ejecting head 10. The liquid ejecting apparatus 1 performs aprinting operation (recording operation) in the first posture P1 shownin FIG. 10 and performs the maintenance operation in the second postureP2 shown in FIG. 11 . That is, the first posture P1 is an example of a“recording posture”, and the second posture P2 is an example of a“maintenance posture”. The printing operation is an example of therecording operation. The “recording operation” means discharging an inkfrom the nozzle N, attaching the ink to a medium, and recording text andan image.

The liquid ejecting apparatus 1 includes the cap 22, a pipe 23, and apump 24 used in a maintenance operation. The cap 22 covers the ejectionsurface F1 of the liquid ejecting head 10. The cap 22 is disposed tocover openings of the nozzles N of the plurality of nozzle rows NL. Aspace 22 a receiving an ink discharged from the nozzles N is formed inthe cap 22.

The pipe 23 is coupled to the cap 22. The pipe 23 is a pipe throughwhich an ink in the space 22 a of the cap 22 is discharged. The pump 24is coupled to the pipe 23. By driving the pump 24, an ink in the cap 22can be sucked and discharged to the outside of the cap 22.

The maintenance operation of the liquid ejecting apparatus 1 includesflushing processing, suction cleaning, and pressurization cleaningprocessing. The maintenance operations are performed in the secondposture P2 of the liquid ejecting head 10. In the flushing processing,an ink that does not contribute to the recording operation is dischargedfrom the nozzle N as pressure fluctuations act on a pressure chamberthat communicates with the nozzle N using an actuator of the liquidejecting head 10. In the suction cleaning processing, for example, anink is sucked from the nozzle N using the pump 24. In addition, in thepressurization cleaning processing, an ink may be discharged from thenozzle N by pressurizing the ink flow path in the liquid ejecting head10 upstream from the pressure chamber using a pump (not shown).

As described above, in the liquid ejecting apparatus 1, an unnecessaryink in the nozzle N can be discharged to the outside of the liquidejecting head 10 by performing maintenance processing. In the secondposture P2 of the liquid ejecting head 10, the ejection surface F1 isparallel to the horizontal plane F0. Since a maintenance operation canbe performed in the second posture P2 in the liquid ejecting apparatus1, the remaining amount of an ink in the cap 22 can be reduced at a timeof air suction in which the pump 24 is driven in a state where a spacein the cap 22 communicates with the atmosphere. For example, when theliquid ejecting head 10 is in the first posture P1, an ink remains in acorner portion 22 c in the cap 22 since the cap 22 is inclined. On theother hand, in the present example, since the maintenance operation isperformed in a state of being disposed along the horizontal plane F0, abottom surface 22 b of the cap 22 can reduce the amount of an inkremaining in the cap 22. When the maintenance operation is performed inthe inclined posture, there is a risk that ink leakage from a sealedportion during capping occurs. The sealed portion during cappingincludes a portion where the cap 22 and the ejection surface F1 are incontact with each other.

In the liquid ejecting apparatus 1, the posture of the liquid ejectinghead 10 can be changed from the first posture P1 to the second postureP2. As described above, when the liquid ejecting head 10 rotationallymoves around the rotation shaft S1, there is a possibility that acentrifugal force and an inertial force caused by the centrifugal forceact on the meniscus of an ink in the nozzle row NL and the meniscusdisintegrates. Since among a plurality of types of inks, the first inkhaving the highest dynamic surface tension is supplied to the nozzle rowNLA which has the largest centrifugal force and the largest inertialforce caused by the centrifugal force, a probability that a meniscusdisintegrates is reduced in the liquid ejecting apparatus 1. Bysuppressing the disintegration of the meniscus, the entry of bubblesinto the nozzle N of the liquid ejecting head 10 is suppressed, or theleakage of an ink from the nozzle N of the nozzle row NLA is suppressed.

Next, the liquid ejecting apparatus 1 according to example 6 will bedescribed with reference to FIG. 12 . In example 6, when the liquidejecting apparatus 1 is mounted on a floor surface 26, an effect of acentrifugal force acting on the nozzle row NL of the liquid ejectinghead 10 will be described. The liquid ejecting head 10 of the liquidejecting apparatus 1 is disposed to be inclined with respect to thehorizontal plane F0. The liquid ejecting apparatus 1 includes thehousing 1 a accommodating the liquid ejecting head 10. The liquidejecting head 10 is held with respect to the housing 1 a. Leg portions 1c and 1 d are provided at a bottom portion of the housing 1 a. The legportions 1 c and 1 d are disposed on the floor surface 26. The floorsurface 26 follows, for example, the horizontal plane F0.

In FIG. 12 , the K-axis direction orthogonal to the gravity direction G1is shown by an arrow when viewed in the X-axis direction. The K-axisdirection follows a right-left direction in FIG. 12 . The leg portions 1c and 1 d are spaced apart from each other in the K-axis direction. Forexample, the K-axis direction follows a longitudinal direction of thehousing 1 a when the liquid ejecting apparatus 1 is viewed in thegravity direction G1. The leg portions 1 c and 1 d may be spaced apartfrom each other in other directions.

The leg portion 1 c includes a contact point Q1, and the leg portion 1 dincludes a contact point Q2. The contact point Q1 is an example of afirst contact point, and the contact point Q2 is an example of a secondcontact point. The contact points Q1 and Q2 are portions in contact withthe floor surface 26 in a state where the housing 1 a is mounted on thefloor surface 26. The contact point Q1 is positioned closer to one end 1e of the housing 1 a in the K-axis direction. The contact point Q2 ispositioned closer to the other end 1 f of the housing 1 a in the K-axisdirection. The one end 1 e of the housing 1 a is an end portion of thehousing 1 a in the K1 direction. The other end 1 f of the housing 1 a isan end portion in the K2 direction.

A center of gravity G of the liquid ejecting apparatus 1 is between thecontact point Q1 and the contact point Q2 in the K-axis direction and ispositioned closer to the contact point Q1 than to the contact point Q2.When viewed in the X-axis direction, a distance UR between the contactpoint Q1 and the nozzle row NLA is larger than a distance DR between thecontact point Q1 and the nozzle row NLB. When viewed in the X-axisdirection, a distance UL between the contact point Q2 and the nozzle rowNLA is larger than a distance DL between the contact point Q2 and thenozzle row NLB. The position of the nozzle row NL is, for example, acenter position of the opening of the nozzle N in the ejection surfaceF1.

In the first posture P1 of the liquid ejecting head 10 shown in FIG. 12, the distance UR is larger than the distance DL. In the first postureof the liquid ejecting head 10, the distance UL is larger than thedistance DR.

For example, when the liquid ejecting apparatus 1 is moved, it isassumed that a plurality of operators hold and move the liquid ejectingapparatus 1 and finally mount the liquid ejecting apparatus 1 on thefloor surface 26. For example, two operators separated from each otherin the K-axis direction can hold the liquid ejecting apparatus 1 fromboth sides. When mounting the liquid ejecting apparatus 1 on the floorsurface 26, one operator closer to the one end 1 e first brings the legportion 1 c into contact with the floor surface 26, and then the otheroperator closer to the other end If brings the leg portion 1 d intocontact with the floor surface 26. In a case where the leg portion 1 cis brought into contact with the floor surface 26 first, the liquidejecting apparatus 1 rotationally moves counterclockwise R1 when viewedin the X-axis direction with the contact point Q1 as a fulcrum. In thiscase, since the distance UR is longer than the distance DR, acentrifugal force that is larger than a centrifugal force acting on thenozzle row NLB acts on the nozzle row NLA.

As described above, when mounting the liquid ejecting apparatus 1 on thefloor surface 26, a centrifugal force and an inertial force caused bythe centrifugal force, which have different magnitudes according to thedistances UR and DR from the contact point Q1, are generated in thenozzle rows NLA and NLB. In the liquid ejecting apparatus 1, the firstink is supplied to the nozzle row NLA, and the second ink is supplied tothe nozzle row NLB. The first ink having a higher dynamic surfacetension is supplied to the nozzle row NLA having a larger centrifugalforce and a larger inertial force, and the second ink having a lowerdynamic surface tension is supplied to the nozzle row NLB having asmaller centrifugal force and a smaller inertial force. Accordingly, aprobability of the disintegration of the meniscus of the first ink inthe nozzle row NLA can be reduced in the liquid ejecting head 10. Thatis, compared to a case where the second ink is supplied to the nozzlerow NLA, a case where the first ink is supplied to the nozzle row NLAhas a low probability of the disintegration of the meniscus.

In the case of the liquid ejecting apparatus 1, since the center ofgravity G of the liquid ejecting apparatus 1 is positioned closer to theleg portion 1 c than the leg portion 1 d in the K-axis direction, thereis a high probability that the operator first brings the leg portion 1 cinto contact with the floor surface 26 before the leg portion 1 d. Sincethe first ink is supplied to the nozzle row NLA as described above, aprobability of the disintegration of the meniscus in the nozzle N of thenozzle row NLA is reduced in the liquid ejecting apparatus 1.

Next, a case where the liquid ejecting apparatus 1 is disposed such thatthe leg portion 1 d is first brought into contact with the floor surface26 before the leg portion 1 c will be described. In a case where the legportion 1 d is brought into contact with the floor surface 26 first, theliquid ejecting apparatus 1 rotationally moves clockwise R2 when viewedin the X-axis direction with the contact point Q2 as a fulcrum. In thiscase, since the distance UL is longer than the distance DL, acentrifugal force, which is larger than a centrifugal force acting onthe nozzle row NLB, and an inertial force caused by the centrifugalforce act on the nozzle row NLA. As described above, when mounting theliquid ejecting apparatus 1 on the floor surface 26, a centrifugal forceand an inertial force caused by the centrifugal force, which havedifferent magnitudes according to the distances UL and DL from thecontact point Q2, are generated in the nozzle rows NLA and NLB. In theliquid ejecting head 10, the first ink having a higher dynamic surfacetension is supplied to the nozzle row NLA having a larger centrifugalforce and a larger inertial force caused by the centrifugal force, andthe second ink having a lower dynamic surface tension is supplied to thenozzle row NLB having a smaller centrifugal force and a smaller inertialforce caused by the centrifugal force. Accordingly, a probability of thedisintegration of the meniscus of the first ink in the nozzle row NLAcan be reduced in the liquid ejecting head 10. That is, compared to acase where the second ink is supplied to the nozzle row NLA, a casewhere the first ink is supplied to the nozzle row NLA has a lowprobability of the disintegration of the meniscus.

For example, in plan view of the liquid ejecting apparatus 1 in thegravity direction G1, a length along the K-axis direction is larger thana length along the X-axis direction. When such a liquid ejectingapparatus 1 is moved, it is easy for the plurality of operators tostrike a balance by holding the liquid ejecting apparatus 1 while beingseparated away in the K-axis direction rather than holding the liquidejecting apparatus 1 while being separated away in the X-axis direction.Since the first ink is assigned to the nozzle row NLA, thedisintegration of the meniscus can be suppressed in the liquid ejectinghead 10 compared to a case where the second ink is assigned to thenozzle row NLA. In the liquid ejecting apparatus 1, the leg portion 1 cmay be lowered first, or the leg portion 1 d may be lowered first.

When moving the liquid ejecting apparatus 1, the plurality of operatorsmay hold the liquid ejecting apparatus 1 while being separated away inthe X-axis direction. Since the nozzle row NLA is positioned above thenozzle row NLB in the gravity direction G1, among contact points betweenthe housing 1 a and the floor surface 26, a distance between a contactpoint positioned most in the X1 direction and the nozzle row NLA islonger than a distance between the contact point and the nozzle row NLB.Similarly, among contact points between the housing 1 a and the floorsurface 26, a distance between a contact point positioned most in the X2direction and the nozzle row NLA is longer than a distance between thecontact point and the nozzle row NLB. Therefore, since the first ink isassigned to the nozzle row NLA regardless of a case of lowering the endportion of the housing 1 a in the X1 direction first or a case oflowering the end portion of the housing 1 a in the X2 direction first,the disintegration of the meniscus can be suppressed.

The liquid ejecting head 10 according to example 6 includes theplurality of nozzle rows NL, each of which extends in the X-axisdirection, but may include the nozzle row NL extending in the directionintersecting the X-axis in plan view of the ejection surface F1 towardthe Z-axis direction. In this case, a distance from a contact point tothe nozzle row NL may be a distance between the contact point and thenozzle N that is most separated from the contact point viewed in theX-axis direction, among the plurality of nozzles N configuring thenozzle row NL.

Next, a measuring method of a dynamic surface tension of an ink andproperties of the ink will be described. The dynamic surface tension ofan ink can be acquired, for example, through a maximum bubble pressuremethod. The measuring method of a dynamic surface tension may be othermeasuring methods, and examples thereof include a suspension method, aWilhelmy method, and an annular method. In the maximum bubble pressuremethod, a tip of a thin tube is immersed with an ink, and a maximumpressure required to release bubbles from the thin tube is measured. Inthe maximum bubble pressure method, bubbles are continuously generatedat the tip of the thin tube, and the maximum pressure is measured.

In the maximum bubble pressure method, when measuring the maximumpressure, a time from a time point when new bubbles are generated at thetip of the thin tube to a time point when the maximum bubble pressure isreached is defined as a lifetime. The maximum bubble pressure is reachedat a time point when the radius of curvature of a bubble and the radiusof the thin tube are equal to each other. The dynamic surface tension ofan ink is a surface tension of the ink in a state where the ink is inmotion. The dynamic surface tension of the ink can be adjusted, forexample, by changing the type and content of a surfactant, awater-soluble organic solvent, and a resin included in the ink.

Hereinafter, although properties of an ink will be described, “part” and“%” regarding the amount of components are based on mass unlessspecified otherwise. FIG. 13 is a table showing components of an ink.

A pigment dispersion liquid 1 will be described. A solution obtained bydissolving 5.0 g of concentrated hydrochloric acid in 5.5 g of water wasbrought into a cooled state of 5° C., and 1.6 g of 4-aminophthalic acidwas added to the solution in this state. A container containing thissolution was placed in an ice bath and was stirred to maintain thetemperature of the solution at 10° C. or lower, and a solution obtainedby dissolving 1.8 g of sodium nitrite in 9.0 g of ion-exchanged water at5° C. was added. After stirring the solution for 15 minutes, 6.0 g ofpigment was added while being stirred, and the solution was furtherstirred for 15 minutes to obtain slurry. The pigment added while beingstirred was carbon black having a specific surface area of 220 m2/g anda DBP oil absorption of 105 mL/100 g. The obtained slurry was filteredthrough filter paper, and particles were sufficiently washed with waterand were dried in an oven at 110° C. Advantech’s product name "standardfilter paper No. 2" was used as the filter paper. After substitutingcounter ions from sodium ions to potassium ions through the ion exchangemethod, an appropriate amount of ion-exchanged water was added to adjusta pigment content, and the pigment dispersion liquid 1 having a pigmentcontent of 20.0% was obtained. The pigment dispersion liquid 1 was usedin preparing the first ink having a black hue.

A pigment dispersion liquid 2 will be described. A styrene-ethylacrylate-acrylic acid copolymer (resin dispersant) having an acid valueof 150 mgKOH/g and a weight average molecular weight of 8,000 wasprepared. The prepared resin dispersant was neutralized with potassiumhydroxide equimolar to the acid value and was dissolved in ion-exchangedwater to prepare an aqueous solution of the resin dispersant having aresin (solid content) content of 20.0%. A mixture was obtained by mixing20.0 parts of pigment (C.I. Pigment Blue 15:3), 30.0 parts of theaqueous solution of the resin dispersant, and 50.0 parts of theion-exchanged water with each other.

The obtained mixture and 200 parts of zirconia beads having a diameterof 0.3 mm were placed in a batch type vertical sand mill (manufacturedby Aimex), were dispersed for 5 hours while cooling with water, and thenwere centrifuged to remove coarse particles. After pressure-filtrationwith a microfilter (manufactured by Fujifilm) having a pore size of 3.0µm, an appropriate amount of ion-exchanged water was added to obtain thepigment dispersion liquid 2. The pigment content of the obtained pigmentdispersion liquid 2 was 20.0%, and a resin dispersant content was 6.0%.The pigment dispersion liquid 2 was used in preparing the second inkhaving a cyan hue.

A pigment dispersion liquid 3 will be described. The pigment dispersionliquid 3 having a pigment content of 20.0% and a resin dispersantcontent of 6.0% was obtained under the same procedures as in the pigmentdispersion liquid 2 described above, except for changing the pigment toC.I. Pigment Yellow 74. The pigment dispersion liquid 3 was used inpreparing the third ink having a yellow hue.

A pigment dispersion liquid 4 will be described. The pigment dispersionliquid 4 having a pigment content of 20.0% and a resin dispersantcontent of 4.0% was obtained under the same procedures as in the pigmentdispersion liquid 2 described above, except for changing to 20.0 partsof pigment (C.I. Pigment Magenta 122), 20.0 parts of the aqueoussolution of the resin dispersant, and 60.0 parts of the ion-exchangedwater. The pigment dispersion liquid 4 was used in preparing the fourthink having a magenta hue.

The adjustment of an ink will be described. After each component (unit:%) indicating the state of table 1 was mixed and sufficiently stirred,pressure-filtration with a cellulose acetate filter (manufactured byAdvantech) having a pore size of 0.8 µm was performed, and each ink wasprepared. In table 1, “Acetylenol E100” and “Acetylenol E60” are productnames of surfactants manufactured by Kawaken Fine Chemicals. The lowerpart of table 1 shows a dynamic surface tension y at a lifetime of 10ms. The dynamic surface tension y was measured using a dynamic surfacetensiometer based on the maximum bubble pressure method under thecondition of 25° C. “BUBBLE PRESSURE TENSIOMETER BP-2”, which is aproduct name of a dynamic surface tensiometer manufactured by KRUSS, wasused as the dynamic surface tensiometer.

Next, disposition of the nozzle rows NL of a liquid ejecting head 10Baccording to modification example 1 will be described with reference toFIG. 14 . FIG. 14 is a bottom view showing an ejection surface F2 of theliquid ejecting head 10B according to modification example 1. The liquidejecting head 10B has the plurality of nozzle rows NL. The nozzle rowsNL include nozzle rows NLA1, NLA2, and NLA3 for ejecting the first ink,nozzle rows NLB1, NLB2, and NLB3 for ejecting the second ink, nozzlerows NLC1, NLC2, and NLC3 for ejecting the third ink, and nozzle rowsNLD1, NLD2, and NLD3 for ejecting the fourth ink. When notdistinguishing between the nozzle rows NLA1, NLA2, NLA3, NLB1, NLB2,NLB3, NLC1, NLC2, NLC3, NLD1, NLD2, and NLD3, the nozzle rows will bedescribed as the nozzle rows NL in some cases. In the liquid ejectinghead 10B, the nozzle row NLA is an example of a first nozzle row, thenozzle row NLB is an example of a second nozzle row, the nozzle row NLCis an example of a third nozzle row, and the nozzle row NLD is anexample of a fourth nozzle row.

The liquid ejecting head 10B has a plurality of head chips 12. The headchip 12 is provided with a nozzle plate in which the nozzle N is formed.The head chip 12 is provided with the nozzle row NL for ejecting onetype of ink. The head chip 12 has a pressure chamber (not shown) and anactuator (not shown). As the actuator raises the pressure of the ink inthe pressure chamber, the ink is ejected from the nozzle N.

The nozzle rows NLA1, NLA2, and NLA3 are disposed at positions differentfrom each other in the X-axis direction. The nozzle rows NLA1 and NLA3and the nozzle row NLA2 are disposed at positions different from eachother in the Y-axis direction. The nozzle row NLA2 is positioned in theY2 direction with respect to the nozzle rows NLA1 and NLA3. In the firstposture P1 of the liquid ejecting head 10B, the nozzle row NLA2 ispositioned above the nozzle rows NLA1 and NLA3 in the gravity directionG1. In the first posture P1, an ejection surface F2 is in a state ofbeing inclined with respect to the horizontal plane.

Disposition of the nozzle rows NLB1, NLB2, and NLB3 is the same as thedisposition of the nozzle rows NLA1, NLA2, and NLA3. The nozzle rowsNLB1, NLB2, and NLB3 and the nozzle rows NLA1, NLA2, and NLA3 are spacedapart from each other in the Y-axis direction.

Disposition of the nozzle rows NLC1, NLC2, and NLC3 is the same as thedisposition of the nozzle rows NLA1, NLA2, and NLA3. The nozzle rowsNLC1, NLC2, and NLC3 are positioned between the nozzle rows NLA1, NLA2,and NLA3 and the nozzle rows NLB1, NLB2, and NLB3 in the Y-axisdirection.

Disposition of the nozzle rows NLD1, NLD2, and NLD3 is the same as thedisposition of the nozzle rows NLA1, NLA2, and NLA3. The nozzle rowsNLD1, NLD2, and NLD3 are positioned between the nozzle rows NLC1, NLC2,and NLC3 and the nozzle rows NLB1, NLB2, and NLB3 in the Y-axisdirection.

The liquid ejecting apparatus 1 may include the liquid ejecting head 10Binstead of the liquid ejecting head 10. The liquid ejecting apparatus 1including the liquid ejecting head 10B achieves the same operationaleffects as the liquid ejecting apparatus 1 including the liquid ejectinghead 10.

Next, disposition of the nozzle rows NL of a liquid ejecting head 10Caccording to modification example 2 will be described with reference toFIG. 15 . FIG. 15 is a bottom view showing an ejection surface F3 of theliquid ejecting head 10C according to modification example 2. The liquidejecting head 10C has the plurality of nozzle rows NL. The nozzle rowsNL include the nozzle row NLA for ejecting the first ink, the nozzle rowNLB for ejecting the second ink, the nozzle row NLC for ejecting thethird ink, and the nozzle row NLD for ejecting the fourth ink. When notdistinguishing between the nozzle rows NLA, NLB, NLC, and NLD, thenozzle rows will be described as the nozzle rows NL in some cases.

The liquid ejecting head 10C has a plurality of head chips 12C. The headchip 12C is provided with a nozzle plate 11C in which the nozzle N isformed. The head chip 12C is provided with each of the nozzle rows NLA,NLB, NLC, and NLD.

FIG. 15 shows a V-axis direction and a W-axis direction that areorthogonal to each other. The V-axis direction and the W-axis directionare orthogonal to the Z-axis direction. The V-axis direction and theW-axis direction are directions having the ejection surface F3 asreference. The V-axis direction includes a V1 direction and a V2direction. The W-axis direction includes a W1 direction and a W2direction. The V-axis direction intersects the X-axis direction at aninclination angle α.

The plurality of nozzle rows NL extend along the V-axis direction. Thenozzles N included in the nozzle row NL are arranged in the V-axisdirection. The nozzle row NLA and the nozzle row NLD are arranged in theV-axis direction. The nozzle row NLA and the nozzle row NLD are spacedapart from each other in the V-axis direction. The nozzle row NLA andthe nozzle row NLD are spaced apart from each other in the Y-axisdirection. In FIG. 15 , imaginary lines L3 and L4 are shown by two-dotchain lines. The imaginary lines L3 and L4 are straight lines that arespaced apart from each other in the Y-axis direction and follow theX-axis direction. The imaginary line L3 is positioned in the Y2direction with respect to the imaginary line L4. The nozzle rows NLA andNLC are positioned in the Y2 direction with respect to the imaginaryline L3, and the nozzle rows NLB and NLD are positioned in the Y1direction with respect to the imaginary line L4.

The nozzle row NLC and the nozzle row NLB are arranged in the V-axisdirection. The nozzle row NLC and the nozzle row NLB are spaced apartfrom each other in the V-axis direction. The nozzle row NLC and thenozzle row NLB are spaced apart from each other in the Y-axis direction.In the liquid ejecting head 10C, the nozzle rows NLA and NLC areexamples of the first nozzle row, and the nozzle rows NLD and NLB areexamples of the second nozzle row.

When viewed in the Y-axis direction, the nozzle row NLA and the nozzlerows NLD and NLB at least partially overlap each other. For example,among two head chips 12C adjacent to each other in the X-axis direction,a head chip disposed in the X1 direction will be defined as a head chip12C1, and a head chip disposed in the X2 direction with respect to thehead chip 12C1 will be defined as a head chip 12C2. When viewed in theY-axis direction, the nozzle row NLA of the head chip 12C1 and thenozzle rows NLD and NLB of the head chip 12C2 at least partially overlapeach other. The nozzle row NLA and the nozzle rows NLD and NLB in thesame head chip 12 may at least partially overlap each other in theY-axis direction.

Similarly, when viewed in the Y-axis direction, the nozzle row NLC andthe nozzle rows NLD and NLB at least partially overlap each other. Whenviewed in the Y-axis direction, the nozzle row NLC of the head chip 12C1and the nozzle rows NLD and NLB of the head chip 12C2 at least partiallyoverlap each other. The nozzle row NLC and the nozzle rows NLD and NLBin the same head chip 12 may at least partially overlap each other inthe Y-axis direction.

When viewed in the X-axis direction, the nozzle row NLA and the nozzlerows NLD and NLB are disposed at intervals in the Y-axis direction. Whenviewed in the X-axis direction, the nozzle row NLC and the nozzle rowsNLD and NLB are disposed at intervals in the Y-axis direction.

In the Y-axis direction, an interval between the nozzle row NLA and thenozzle row NLC that are provided in the same head chip 12C is narrowerthan an interval between the nozzle row NLC provided in the head chip12C1 and the nozzle row NLA provided in the head chip 12C2.

A nozzle NA1 positioned at an upper end of the nozzle row NLA in thegravity direction G1 is positioned above a nozzle ND1 positioned at anupper end of the nozzle row NLD and a nozzle NB1 positioned at an upperend of the nozzle row NLB in the gravity direction G1.

A nozzle NC1 positioned at an upper end of the nozzle row NLC in thegravity direction G1 is positioned above the nozzle ND1 positioned atthe upper end of the nozzle row NLD and the nozzle NB1 positioned at theupper end of the nozzle row NLB in the gravity direction G1.

The liquid ejecting apparatus 1 including such a liquid ejecting head10C achieves the same operational effects as the liquid ejectingapparatus 1 including the liquid ejecting head 10.

When an effect of variations in the water head difference describedabove is considered as a problem in the liquid ejecting head 10Cincluding the nozzle rows NL at least partially overlapping each otherin the gravity direction G1, it is desirable to determine a heightrelationship between the nozzle rows NL at least partially overlappingeach other by comparing the positions of the nozzles N at the upper endsof the respective nozzle rows NL in the gravity direction G1. This isbecause the nozzle N positioned at the upper end of the nozzle row NL isthe nozzle N to which an ink is most difficult to be supplied due to awater head difference. Thus, it is desirable to compare the heights ofthe nozzles N positioned at the upper ends such that the first ink canbe supplied to the nozzle N to which the ink is most difficult to besupplied.

As shown in FIG. 15 , the liquid ejecting head 10C includes the nozzlerow NLA and the nozzle row NLC at least partially overlapping each otherin the gravity direction G1 and the nozzle row NLB and the nozzle rowNLD at least partially overlapping each other in the gravity directionG1. Since the nozzle NA1 positioned at the upper end of the nozzle rowNLA is positioned above the nozzle NC1 positioned at the upper end ofthe nozzle row NLC and the nozzle ND1 positioned at the upper end of thenozzle row NLD is positioned above the nozzle NB1 positioned at theupper end of the nozzle row NLB, the nozzle row NLA may be an example ofthe first nozzle row, the nozzle row NLB may be an example of the secondnozzle row, the nozzle row NLC may be an example of the third nozzlerow, and the nozzle row NLD may be an example of the fourth nozzle row.

When color mixing caused by a plurality of types of ink droplets beingoverflowed from each nozzle row NL along the ejection surface F3described above is considered as a problem in the liquid ejecting head10C including the nozzle rows NL at least partially overlapping eachother in the gravity direction G1, it is desirable to determine a heightrelationship between the nozzle rows NL at least partially overlappingeach other by comparing the nozzles N positioned at the same position onan X-axis in an extending direction of an intersection line between theejection surface F3 in the inclined posture of each nozzle row NL andthe horizontal plane F0. This is because the intersection line betweenthe ejection surface F3 in the inclined posture and the horizontal planeF0 follows the X-axis. Thus, an ink overflowed from the nozzle N tendsto drip on the ejection surface F3 in the Y1 direction by the action ofgravity.

In addition, a problem of color mixing caused by dripping of an ink islikely to occur in the same head chip 12C. In the present modificationexample, in the same head chip 12C, the nozzle row NLA and the nozzlerow NLC at least partially overlap each other in the gravity directionG1, and the nozzle row NLB and the nozzle row NLD at least partiallyoverlap each other in the gravity direction G1.

Herein, when the nozzle NA of the nozzle row NLA and the nozzle NC ofthe nozzle row NLC that are positioned in the same head chip 12C and areat the same position on the X-axis are compared to each other, since thenozzle NA of the nozzle row NLA is positioned above the nozzle NC of thenozzle row NLC, the nozzle row NLA may be a nozzle row above the nozzlerow NLC. Similarly, when the nozzle ND of the nozzle row NLD and thenozzle NB of the nozzle row NLB that are positioned in the same headchip 12C and are at the same position on the X-axis are compared to eachother, since the nozzle ND of the nozzle row NLD is positioned above thenozzle NB of the nozzle row NLB, the nozzle row NLD may be a nozzle rowabove the nozzle row NLB. As described above, the nozzle row NLA may bean example of the first nozzle row, the nozzle row NLB may be an exampleof the second nozzle row, the nozzle row NLC may be an example of thethird nozzle row, and the nozzle row NLD may be an example of the fourthnozzle row.

Next, disposition of the nozzle rows NL of a liquid ejecting head 10Daccording to modification example 3 will be described with reference toFIG. 16 . FIG. 16 is a bottom view showing an ejection surface F4 of theliquid ejecting head 10D according to modification example 3. The liquidejecting head 10D has the plurality of nozzle rows NL. The nozzle rowsNL includes the nozzle row NLA for ejecting the first ink and the nozzlerow NLB for ejecting the second ink. When not distinguishing between thenozzle rows NLA and NLB, the nozzle rows will be described as the nozzlerows NL in some cases.

The liquid ejecting head 10D has a plurality of head chips 12D. The headchip 12D is provided with a nozzle plate 11D in which the nozzle N isformed. The head chip 12D is provided with each of the nozzle rows NLAand NLB.

The plurality of nozzle rows NL extend along the V-axis direction. Thenozzles N included in the nozzle row NL are arranged in the V-axisdirection. The nozzle rows NLA and NLB are disposed at positionsdifferent from each other in the W-axis direction. When viewed in theW-axis direction, the nozzle rows NLA and NLB at least partially overlapeach other. When viewed in the Y-axis direction, the nozzle row NLA andthe nozzle row NLB at least partially overlap each other. When viewed inthe X-axis direction, the nozzle row NLA and the nozzle row NLB at leastpartially overlap each other.

When viewed in the X-axis direction, the nozzle row NLA and the nozzlerow NLB at least partially overlap each other, that is, the nozzle rowNLA and the nozzle row NLB at least partially overlap each other in thegravity direction G1. The nozzle NA1 positioned at the upper end of thenozzle row NLA in the gravity direction G1 is positioned above thenozzle NB1 positioned at the upper end of the nozzle row NLB in thegravity direction G1.

In addition, when the nozzle NA of the nozzle row NLA and the nozzle NBof the nozzle row NLB that are positioned in the same head chip 12D andare at the same position on the X-axis are compared to each other, thenozzle NA of the nozzle row NLA is positioned above the nozzle NB of thenozzle row NLB. For this reason, even when considering any one of aproblem of variations in a water head difference between the pressureadjusting portion 8 and the nozzle row NL and a problem of overflowingof an ink on the ejection surface F4 and occurrence of color mixing, thenozzle row NLA may be an example of the first nozzle row, and the nozzlerow NLB may be an example of the second nozzle row in the liquidejecting head 10D, as in modification example 2 described above.

In FIG. 16 , imaginary lines L5 and L6 are shown by two-dot chain lines.The imaginary lines L5 and L6 are straight lines that are spaced apartfrom each other in the Y-axis direction and follow the X-axis direction.The imaginary line L5 is positioned in the Y2 direction with respect tothe imaginary line L6. When viewed in the Z-axis direction, theimaginary line L5 overlaps the nozzle NA1, and the imaginary line L6overlaps the nozzle NB1. The nozzle row NLA includes a portion disposedin the Y2 direction with respect to the imaginary line L6.

The liquid ejecting apparatus 1 including such a liquid ejecting head10D achieves the same operational effects as the liquid ejectingapparatus 1 including the liquid ejecting head 10.

Next, disposition of the nozzle rows NL of liquid ejecting heads 10G and10H according to modification example 4 will be described with referenceto FIG. 17 . FIG. 17 is a bottom view showing ejection surfaces of theliquid ejecting heads 10G and 10H according to modification example 4.The liquid ejecting apparatus 1 shown in FIG. 1 may include a head unit20 having a plurality of liquid ejecting heads 10G and 10H instead ofthe liquid ejecting head 10. The head unit 20 has the plurality ofliquid ejecting heads 10G and 10H alternately arranged in the X-axisdirection. FIG. 17 shows the plurality of liquid ejecting heads 10G andthe liquid ejecting head 10H disposed between the plurality of liquidejecting heads 10G.

The liquid ejecting head 10G includes, as the plurality of nozzle rowsNL, the nozzle row NLA1 for ejecting the first ink, the nozzle row NLB1for ejecting the second ink, the nozzle row NLC1 for ejecting the thirdink, and the nozzle row NLD1 for ejecting the fourth ink.

The liquid ejecting head 10G has a plurality of head chips 12G1, 12G2,12G3, and 12G4. The head chip 12G1 is provided with the nozzle row NLA1,the head chip 12G2 is provided with the nozzle row NLB1, the head chip12G3 is provided with the nozzle row NLC1, and the head chip 12G4 isprovided with the nozzle row NLD1.

In the liquid ejecting head 10G, the nozzle row NLA1 is an example ofthe first nozzle row, the nozzle row NLB1 is an example of the secondnozzle row, the nozzle row NLC1 is an example of the third nozzle row,and the nozzle row NLD1 is an example of the fourth nozzle row. Theplurality of nozzle rows NLA1, NLB1, NLC1, and NLD1 extend in the X-axisdirection. The nozzle row NLA1, the nozzle row NLC1, the nozzle rowNLD1, and the nozzle row NLB1 are disposed in this order in the Y1direction. The nozzle row NLB1 is longer than the nozzle row NLD1regarding the X-axis direction. The nozzle row NLD1 is longer than thenozzle row NLC1 regarding the X-axis direction. The nozzle row NLC1 islonger than the nozzle row NLA1 regarding the X-axis direction. Thenozzle row NLB1 is longer than the nozzle row NLA1 regarding the X-axisdirection. In an inclined posture of the head unit 20, the nozzle rowNLA1 is disposed at a position higher than the nozzle row NLC1, thenozzle row NLC1 is disposed at a position higher than the nozzle rowNLD1, and the nozzle row NLD1 is disposed at a position higher than thenozzle row NLB1.

The liquid ejecting head 10H includes, as the plurality of nozzle rowsNL, the nozzle row NLA2 for ejecting the first ink, the nozzle row NLB2for ejecting the second ink, the nozzle row NLC2 for ejecting the thirdink, and the nozzle row NLD2 for ejecting the fourth ink.

The liquid ejecting head 10H has a plurality of head chips 12H1, 12H2,12H3, and 12H4. The head chip 12H1 is provided with the nozzle row NLA2,the head chip 12H2 is provided with the nozzle row NLB2, the head chip12H3 is provided with the nozzle row NLC2, and the head chip 12H4 isprovided with the nozzle row NLD2.

In the liquid ejecting head 10H, the nozzle row NLA2 is an example ofthe first nozzle row, the nozzle row NLB2 is an example of the secondnozzle row, the nozzle row NLC2 is an example of the third nozzle row,and the nozzle row NLD2 is an example of the fourth nozzle row. Theplurality of nozzle rows NLA2, NLB2, NLC2, and NLD2 extend in the X-axisdirection. The nozzle row NLA2, the nozzle row NLC2, the nozzle rowNLD2, and the nozzle row NLB2 are disposed in this order in the Y1direction. The nozzle row NLA2 is longer than the nozzle row NLC2regarding the X-axis direction. The nozzle row NLC2 is longer than thenozzle row NLD2 regarding the X-axis direction. The nozzle row NLD2 islonger than the nozzle row NLB2 regarding the X-axis direction. Thenozzle row NLA2 is longer than the nozzle row NLB2 regarding the X-axisdirection. In the inclined posture of the head unit 20, the nozzle rowNLA2 is disposed at a position higher than the nozzle row NLC2, thenozzle row NLC2 is disposed at a position higher than the nozzle rowNLD2, and the nozzle row NLD2 is disposed at a position higher than thenozzle row NLB2.

The liquid ejecting apparatus 1 including such liquid ejecting heads 10Gand 10H achieves the same operational effects as the liquid ejectingapparatus 1 including the liquid ejecting head 10.

Next, a liquid ejecting apparatus 1B according to a second embodimentwill be described with reference to FIG. 18 . FIG. 18 is a schematicview showing the liquid ejecting apparatus 1B according to the secondembodiment. The liquid ejecting apparatus 1B includes a plurality ofliquid ejecting heads 30A to 30E, a drum 35 that transports the mediumPA, and pressure adjusting portions 38A to 38E. In the description ofthe second embodiment, the same description as in the first embodimentwill be omitted. As described above, the X-axis direction, the Y-axisdirection, and the Z-axis direction, which are shown in each drawing,differ according to the postures of the liquid ejecting heads 30A to30E. The drum 35 may be an intermediate transfer body on which an inkejected from the liquid ejecting heads 30A to 30E lands.

The drum 35 rotates around a rotation shaft 35 a extending in the X-axisdirection. The medium PA is transported with the rotation of the drum35. The medium PA passes through positions corresponding to the liquidejecting heads 30A to 30E. An ink is ejected from the liquid ejectingheads 30A to 30E to the moving medium PA.

The plurality of liquid ejecting heads 30A to 30E are disposed atpositions different from each other in a circumferential direction ofthe drum 35. Ejection surfaces F31 to F35 of the liquid ejecting heads30A to 30E are disposed at angles different from each other. Theejection surfaces F31 to F35 are surfaces of nozzle plates.

FIG. 19 is a schematic view showing the posture of the liquid ejectinghead 30A. The liquid ejecting head 30A has the nozzle row NLA forejecting the first ink. The nozzle row NLA is formed on the ejectionsurface F31 of the liquid ejecting head 30A. The plurality of nozzles NAincluded in the nozzle row NLA are arranged in the X-axis direction. AnLA direction perpendicular to the ejection surface F31 follows thegravity direction G1. An ink ejected from the nozzles NA of the liquidejecting head 30A flies downward along the gravity direction G1.

FIG. 20 is a schematic view showing the posture of the liquid ejectinghead 30B. The liquid ejecting head 30B has the nozzle row NLB forejecting the second ink. The nozzle row NLB is formed on the ejectionsurface F32 of the liquid ejecting head 30B. The plurality of nozzles NBincluded in the nozzle row NLB are arranged in the X-axis direction. AnLB direction perpendicular to the ejection surface F32 follows thegravity direction G1. FIG. 20 shows the upward direction G2 that is anopposite direction to the gravity direction G1. An ink ejected from thenozzles NB of the liquid ejecting head 30B flies in the upward directionG2.

The liquid ejecting head 30A is an example of a first liquid ejectinghead, and the liquid ejecting head 30B is an example of a second liquidejecting head. The ejection surface F31 is an example of a firstejection surface, and the ejection surface F32 is an example of a secondejection surface. The nozzle NA is an example of a first nozzle thatejects the first ink, and the nozzle NB is an example of a second nozzlethat ejects the second ink. The dynamic surface tension of the first inkis higher than the dynamic surface tension of the second ink.

In the liquid ejecting head 30A shown in FIG. 19 , an angle β1 formed byan ejection direction of the first ink ejected from the nozzle NA andthe gravity direction G1 is 0 degree. The angle β1 is an example of afirst angle. In the liquid ejecting head 30B shown in FIG. 20 , an angleβ2 formed by an ejection direction of the second ink ejected from thenozzle NB and the gravity direction G1 is 180 degrees. The angle β2 isan example of a second angle. The angle β2 is an angle larger than theangle β1.

FIG. 21 is a schematic view showing the posture of the liquid ejectinghead 30C. The liquid ejecting head 30C has the nozzle row NLC forejecting the third ink. The nozzle row NLC is formed on the ejectionsurface F33 of the liquid ejecting head 30C. The plurality of nozzles NCincluded in the nozzle row NLC are arranged in the X-axis direction. AnLC direction perpendicular to the ejection surface F33 follows the K1direction orthogonal to the gravity direction G1. FIG. 21 shows the K1direction orthogonal to the gravity direction G1. An ink ejected fromthe nozzles NC of the liquid ejecting head 30C flies along the K1direction orthogonal to the gravity direction G1.

The liquid ejecting head 30C is an example of a third liquid ejectinghead. The ejection surface F33 is an example of a third ejectionsurface. The nozzle NC is an example of a third nozzle that ejects thethird ink. The dynamic surface tension of the third ink is lower thanthe dynamic surface tension of the first ink and is higher than thedynamic surface tension of the second ink.

An angle β3 formed by the K1 direction, which is an ejection directionof the third ink ejected from the nozzle NC, and the gravity directionG1 is 90 degrees. The angle β3 is an example of a third angle. The angleβ3 is an angle larger than the angle β1 and is an angle smaller than theangle β2.

FIG. 22 is a schematic view showing the posture of the liquid ejectinghead 30D. The liquid ejecting head 30D has the nozzle row NLD forejecting the fourth ink. The nozzle row NLD is formed on the ejectionsurface F34 of the liquid ejecting head 30D. The plurality of nozzles NDincluded in the nozzle row NLD are arranged in the X-axis direction. AnLD direction perpendicular to the ejection surface F34 follows adirection intersecting the gravity direction G1 and the K-axisdirection. An ink ejected from the nozzles ND of the liquid ejectinghead 30D flies in the direction intersecting the gravity direction G1and the K-axis direction, that is, obliquely upward along the Z1direction in FIG. 22 .

The liquid ejecting head 30D is an example of a fourth liquid ejectinghead. The ejection surface F34 is an example of a fourth ejectionsurface. The nozzle ND is an example of a fourth nozzle that ejects thefourth ink. The dynamic surface tension of the fourth ink is lower thanthe dynamic surface tension of the third ink and is higher than thedynamic surface tension of the second ink.

An angle β4 formed by an ejection direction of the fourth ink ejectedfrom the nozzle ND, which is the Z1 direction in FIG. 22 , and thegravity direction G1 is 135 degrees. The angle β4 is an example of afourth angle. The angle β4 is an angle larger than the angle β3 and isan angle smaller than the angle β2.

FIG. 23 is a schematic view showing the posture of the liquid ejectinghead 30E. The liquid ejecting head 30E has the nozzle row NLE forejecting a fifth ink. The nozzle row NLE is formed on the ejectionsurface F35 of the liquid ejecting head 30E. The plurality of nozzles NEincluded in the nozzle row NLE are arranged in the X-axis direction. AnLE direction perpendicular to the ejection surface F35 follows adirection intersecting the gravity direction G1 and the K-axisdirection. An ink ejected from the nozzles NE of the liquid ejectinghead 30E flies in the direction intersecting the gravity direction G1and the K-axis direction, that is, obliquely downward along the Z1direction in FIG. 23 .

The liquid ejecting head 30E is an example of a fifth liquid ejectinghead. The ejection surface F35 is an example of a fifth ejectionsurface. The nozzle NE is an example of a fifth nozzle that ejects thefifth ink. The dynamic surface tension of the fifth ink is lower thanthe dynamic surface tension of the first ink and is higher than thedynamic surface tension of the third ink.

An angle β5 formed by an ejection direction of the fifth ink ejectedfrom the nozzle NE, which is the Z1 direction in FIG. 23 , and thegravity direction G1 is 45 degrees. The angle β5 is an example of afifth angle. The angle β5 is an angle larger than the angle β1 and is anangle smaller than the angle β3.

Next, the water head differences H1 to H5 of the nozzle rows NLA to NLEwill be described with reference to FIG. 18 . The pressure adjustingportion 38A is coupled to the nozzle row NLA via an ink flow path 37.The pressure adjusting portion 38B is coupled to the nozzle row NLB viathe ink flow path 37. The pressure adjusting portion 38C is coupled tothe nozzle row NLC via the ink flow path 37. The pressure adjustingportion 38D is coupled to the nozzle row NLD via the ink flow path 37.The pressure adjusting portion 38E is coupled to the nozzle row NLE viathe ink flow path 37.

The pressure adjusting portions 38A to 38E can use the sameconfiguration as the pressure adjusting portion 8 described in the firstembodiment. In addition, as in the first embodiment, the pressureadjusting portions 38A to 38E have the same configuration. The pressureadjusting portion 38A adjusts the pressure of the first ink. Thepressure adjusting portion 38B adjusts the pressure of the second ink.The pressure adjusting portion 38C adjusts the pressure of the thirdink. The pressure adjusting portion 38D adjusts the pressure of thefourth ink. The pressure adjusting portion 38E adjusts the pressure ofthe fifth ink.

FIG. 18 shows the height position H0 of each of the pressure adjustingportions 38A to 38E in the gravity direction G1. The height position H0is positioned above the height positions HA, HB, HC, HD, and HE of thenozzle rows NLA, NLB, NLC, NLD, and NLE. The height position HA isdisposed at a position higher than the height position HE. The heightposition HE is disposed at a position higher than the height positionHC. The height position HC is disposed at a position higher than theheight position HD. The height position HD is disposed at a positionhigher than the height position HB.

The water head difference H2 between the pressure adjusting portion 38Band the nozzle row NLB is larger than the water head difference H4between the pressure adjusting portion 38D and the nozzle row NLD. Thewater head difference H4 is larger than the water head difference H3between the pressure adjusting portion 38C and the nozzle row NLC. Thewater head difference H3 is larger than the water head difference H5between the pressure adjusting portion 38E and the nozzle row NLE. Thewater head difference H5 is larger than the water head difference H1between the pressure adjusting portion 38A and the nozzle row NLA. Thatis, the water head difference H2 is larger than the water headdifference H4, the water head difference H4 is larger than the waterhead difference H3, the water head difference H3 is larger than thewater head difference H5, and the water head difference H5 is largerthan the water head difference H1.

Even such a liquid ejecting apparatus 1B according to the secondembodiment achieves the same operational effects as the liquid ejectingapparatus 1 of the first embodiment.

In the liquid ejecting apparatus 1B, positions of the nozzles NA, NB,NC, ND, and NE of the nozzle rows NLA, NLB, NLC, NLD, and NLE aredifferent according to the dynamic surface tension of an ink. The nozzleNA of the nozzle row NLA for ejecting the first ink having the highestdynamic surface tension is disposed at a position higher than thenozzles NB, NC, ND, and NE of the other nozzle rows NLB, NLC, NLD, andNLE in the gravity direction G1. That is, the first ink that is easierto be supplied is supplied to the nozzle NA of the nozzle row NLA whichhas the small water head difference H1 and to which the ink is difficultto be supplied.

In the liquid ejecting apparatus 1B, the nozzle NB of the nozzle row NLBfor ejecting the second ink having the lowest dynamic surface tension isdisposed at a position lower than the nozzles NA, NC, ND, and NE of theother nozzle rows NLA, NLC, NLD, and NLE in the gravity direction G1.The second ink that is more difficult to be ejected and supplied issupplied to the nozzle NB of the nozzle row NLB which has the largewater head difference H2 and to which the ink is easy to be supplied.

In the liquid ejecting apparatus 1B, since the nozzle NA of the nozzlerow NLA for ejecting the first ink having a higher dynamic surfacetension is positioned above the nozzle NB of the nozzle row NLB forejecting the second ink having a lower dynamic surface tension in thegravity direction G1, variations in supply characteristics of an ink tothe plurality of nozzle rows NL for ejecting different types of inks canbe reduced, and variations in ejection characteristics of an ink in theplurality of nozzle rows NL can be suppressed. As a result, the printingaccuracy of the liquid ejecting apparatus 1B can be improved.

In the liquid ejecting apparatus 1B, the nozzle NC of the nozzle row NLCfor ejecting the third ink is positioned between the nozzle NA of thenozzle row NLA and the nozzle NB of the nozzle row NLB in the gravitydirection G1. The third ink having a dynamic surface tension lower thanthe first ink is supplied to the nozzle NC of the nozzle row NLC havingthe water head difference H3 larger than the water head difference H1.The third ink having a dynamic surface tension higher than the secondink is supplied to the nozzle NC of the nozzle row NLC having the waterhead difference H3 smaller than the water head difference H2.

In the liquid ejecting apparatus 1B, the nozzle ND of the nozzle row NLDfor ejecting the fourth ink is positioned between the nozzle NC of thenozzle row NLC and the nozzle NB of the nozzle row NLB in the gravitydirection G1. The fourth ink having a dynamic surface tension lower thanthe third ink is supplied to the nozzle ND of the nozzle row NLD havingthe water head difference H4 larger than the water head difference H3.The fourth ink having a dynamic surface tension higher than the secondink is supplied to the nozzle ND of the nozzle row NLD having the waterhead difference H4 smaller than the water head difference H2.

In the liquid ejecting apparatus 1B, the nozzle NE of the nozzle row NLEfor ejecting the fifth ink is positioned between the nozzle NA of thenozzle row NLA and the nozzle NC of the nozzle row NLC in the gravitydirection G1. The fifth ink having a dynamic surface tension lower thanthe first ink is supplied to the nozzle NE of the nozzle row NLE havingthe water head difference H5 larger than the water head difference H1.The fifth ink having a dynamic surface tension higher than the third inkis supplied to the nozzle NE of the nozzle row NLE having the water headdifference H5 smaller than the water head difference H3.

Since the height positions of the nozzles NA to NE are different fromeach other according to the dynamic surface tension of an ink in such aliquid ejecting apparatus 1B, variations in supply characteristics of anink to the plurality of nozzles NA to NE for ejecting different types ofinks can be reduced, and variations in ejection characteristics of anink in the plurality of nozzles NA to NE can be suppressed. As a result,the printing accuracy of the liquid ejecting apparatus 1B can beimproved.

Although the height position H0 of each of the pressure adjustingportions 38A to 38E is positioned above the height positions HA, HB, HC,HD, and HE of the nozzles NA, NB, NC, ND, and NE in the gravitydirection G1 in the present embodiment, the height position H0 is notlimited thereto. The height position H0 may be positioned between theheight position HA and the height position HB in the gravity directionG1 or may be positioned below the height positions HA, HE, HC, HD, andHB.

The embodiments described above are merely representative forms of thepresent disclosure. The present disclosure is not limited to theembodiments described above, and various changes and additions arepossible without departing from the gist of the present disclosure.

Although a plurality of inks having colors different from each other aregiven as examples in the embodiments described above, the inks are notlimited thereto. For example, the first ink and the second ink may havedynamic surface tensions different from each other and may have the samecolor.

Although the line type liquid ejecting apparatus 1 including a line headis given as an example in the embodiments described above, the presentdisclosure may also be applied to a serial type liquid ejectingapparatus in which a carriage, on which the liquid ejecting head 10 ismounted, is reciprocated in the width direction of the medium PA.

The liquid ejecting apparatus 1 that is given as an example in theembodiments described above can be adopted in various types of devicessuch as a facsimile device and a copier in addition to a devicededicated to printing. However, the application of the liquid ejectingapparatus of the embodiments of the present disclosure is not limited toprinting. For example, a liquid ejecting apparatus that discharges acolor material solution is used as a manufacturing device that forms acolor filter of a display device such as a liquid crystal display panel.In addition, a liquid ejecting apparatus that discharges a conductivematerial solution is used as a manufacturing device that forms wiringand an electrode of a wiring substrate. In addition, a liquid ejectingapparatus that discharges an organic substance solution related to aliving body is used, for example, as a manufacturing device thatmanufactures a biochip.

What is claimed is:
 1. A liquid ejecting apparatus comprising: a liquidejecting head that has an ejection surface including a first nozzle rowconfigured to eject a first ink and a second nozzle row configured toeject a second ink, wherein the liquid ejecting head is configured to beheld in a first posture in which the ejection surface is inclined withrespect to a horizontal plane, a dynamic surface tension of the firstink is higher than a dynamic surface tension of the second ink, and inthe first posture, the first nozzle row is positioned above the secondnozzle row with respect to a gravity direction.
 2. The liquid ejectingapparatus according to claim 1, wherein a difference between the dynamicsurface tension of the first ink and the dynamic surface tension of thesecond ink is 1.0 mN/m or larger.
 3. The liquid ejecting apparatusaccording to claim 1, wherein a dynamic surface tension of the first inkat a lifetime of 10 msec is higher than a dynamic surface tension of thesecond ink at a lifetime of 10 msec.
 4. The liquid ejecting apparatusaccording to claim 1, wherein the first nozzle row and the second nozzlerow are formed on a common nozzle plate.
 5. The liquid ejectingapparatus according to claim 4, wherein in a case where a direction inwhich an intersection line between the ejection surface in the firstposture and the horizontal plane extends is defined as a first directionand a direction orthogonal to the first direction in the ejectionsurface is defined as a second direction, the first nozzle row and thesecond nozzle row at least partially overlap each other when viewed inthe second direction.
 6. The liquid ejecting apparatus according toclaim 1, wherein a direction in which an intersection line between theejection surface in the first posture and the horizontal plane extendsis defined as a first direction, and the first nozzle row and the secondnozzle row are disposed at an interval when viewed in the firstdirection.
 7. The liquid ejecting apparatus according to claim 1,wherein a nozzle positioned at an upper end of the first nozzle row withrespect to the gravity direction is positioned above, with respect tothe gravity direction, a nozzle positioned at an upper end of the secondnozzle row with respect to the gravity direction.
 8. The liquid ejectingapparatus according to claim 1, wherein the ejection surface furtherincludes a third nozzle row configured to eject a third ink, a dynamicsurface tension of the third ink is lower than the dynamic surfacetension of the first ink and is higher than the dynamic surface tensionof the second ink, and in the first posture, the third nozzle row ispositioned below the first nozzle row and above the second nozzle rowwith respect to the gravity direction.
 9. The liquid ejecting apparatusaccording to claim 8, wherein the ejection surface further includes afourth nozzle row configure to eject a fourth ink, a dynamic surfacetension of the fourth ink is higher than the dynamic surface tension ofthe second ink and is lower than the dynamic surface tension of thethird ink, and in the first posture, the fourth nozzle row is positionedbelow the third nozzle row and above the second nozzle row with respectto the gravity direction.
 10. The liquid ejecting apparatus according toclaim 1, wherein a posture of the liquid ejecting head is configured tobe changed to a plurality of postures including the first posture and asecond posture different from the first posture, the liquid ejectinghead is configured to rotate around a rotation shaft along a firstdirection which is an extending direction of an intersection linebetween the ejection surface in the first posture and the horizontalplane, and in a case where a line that passes through a center betweenthe first nozzle row and the second nozzle row in the first posture andextends in a direction perpendicular to the ejection surface in thefirst posture when viewed in the first direction is defined as a firstimaginary line, the rotation shaft is positioned on a second nozzle rowside when viewed from the first imaginary line.
 11. The liquid ejectingapparatus according to claim 10, wherein the first posture is arecording posture in which a recording operation is performed byejecting the first ink and the second ink to a medium, and the secondposture is a maintenance posture in which maintenance of the liquidejecting head is performed.
 12. The liquid ejecting apparatus accordingto claim 10, wherein in the second posture, the ejection surface isparallel to the horizontal plane.
 13. The liquid ejecting apparatusaccording to claim 1, further comprising: a housing that accommodatesthe liquid ejecting head, wherein the housing has a first contact pointthat is a portion which is in contact with a floor surface in a statewhere the housing is mounted on the floor surface when viewed in a firstdirection, which is an extending direction of an intersection linebetween the ejection surface in the first posture and the horizontalplane, and that is positioned at one end in a third direction orthogonalto both of the first direction and the gravity direction when viewed inthe first direction, and in the first posture, a distance between thefirst contact point and the first nozzle row is larger than a distancebetween the first contact point and the second nozzle row.
 14. Theliquid ejecting apparatus according to claim 13, wherein the housing hasa second contact point that is the portion which is in contact with thefloor surface in a state of being mounted on the floor surface whenviewed in the first direction and that is positioned at the other end inthe third direction, and when viewed in the first direction, a center ofgravity of the liquid ejecting apparatus is closer to the first contactpoint than to the second contact point with respect to the thirddirection.
 15. The liquid ejecting apparatus according to claim 13,wherein the housing has a second contact point that is the portion whichis in contact with the floor surface in a state of being mounted on thefloor surface when viewed in the first direction and that is positionedat the other end in the third direction, and in the first posture, adistance between the second contact point and the first nozzle row islarger than a distance between the second contact point and the secondnozzle row.
 16. The liquid ejecting apparatus according to claim 1,further comprising: a first pressure adjusting portion that adjusts apressure of the first ink to be supplied to the first nozzle row; and asecond pressure adjusting portion that adjusts a pressure of the secondink to be supplied to the second nozzle row, wherein the first pressureadjusting portion and the second pressure adjusting portion are disposedat the same position with respect to the gravity direction.
 17. A liquidejecting apparatus comprising: a first liquid ejecting head that has afirst ejection surface including a first nozzle configured to eject afirst ink; and a second liquid ejecting head that has a second ejectionsurface including a second nozzle configured to eject a second ink,wherein a dynamic surface tension of the first ink is higher than adynamic surface tension of the second ink, the first ejection surface isdisposed such that an angle formed by an ejection direction of the firstink ejected from the first nozzle and a gravity direction is a firstangle, and the second ejection surface is disposed such that an angleformed by an ejection direction of the second ink ejected from thesecond nozzle and the gravity direction is a second angle larger thanthe first angle.
 18. The liquid ejecting apparatus according to claim17, further comprising: a first pressure adjusting portion that adjustsa pressure of the first ink to be supplied to the first nozzle; and asecond pressure adjusting portion that adjusts a pressure of the secondink to be supplied to the second nozzle, wherein the first pressureadjusting portion and the second pressure adjusting portion are disposedat the same position with respect to the gravity direction.
 19. A liquidejecting head comprising: a first nozzle row configure to eject a firstink; a second nozzle row configured to eject a second ink; and a thirdnozzle row configured to eject a third ink, wherein a dynamic surfacetension of the third ink is lower than a dynamic surface tension of thefirst ink and is higher than a dynamic surface tension of the secondink, and the third nozzle row is positioned between the first nozzle rowand the second nozzle row.